1. Field of the Invention
The present invention relates to a method of manufacturing a crystalline semiconductor material in which an amorphous semiconductor material is crystallized by a heat treatment and to a method of manufacturing a semiconductor device using the same.
2. Description of the Related Art
Currently, especially in a field of FPD (Flat Panel Display), research and development have been actively proceeded on manufacturing thin film transistors (TFT) using a polycrystalline silicon (polysilicon) film at a low temperature by excimer laser annealing (ELA). Also, early realization of a system on a panel in which LSI (Large Scale Integrated Circuit) is mounted on any substrate is expected. It is necessary to improve the performance of the TFT using the polysilicon (Si) film in a low-temperature process. In order to improve the performance, improvement in crystallinity and increase in grain size of the polysilicon film have been studied.
However, the grain size of the polysilicon film increases and becomes large as the channel length of the TFT, the crystal property of the polysilicon film becomes nonuniform. Therefore, to solve the problem, the utilization of a quasi-single crystal phase in which the neighboring grain boundaries are partially matched, which is more like a single crystal phase than a polycrystal phase is proposed (Japanese Patent Application Laid-open Hei 11-145056). By using the quasi-single crystalline silicon film, scattering barriers of the carrier in the grain boundary can be lowered compared to using the polysilicon film. As a result, the performance of the TFT can be improved.
However, the scattering barrier of the carrier also exist in the grain boundary in the quasi-single crystalline silicon film. Therefore, the uniformity and the improvement in the performance of the TFT cannot be sufficiently achieved. In order to achieve a uniform and high performance TFT, the further lattice matching of the neighboring grain boundaries is required to further improve the crystallinity.
The invention has been designed to overcome the foregoing problems. The object of the invention is to provide a method of manufacturing a crystalline semiconductor material capable of improving the crystallinity and a method of manufacturing a semiconductor device using the same.
A method of manufacturing a crystalline semiconductor material and a semiconductor device of the invention each includes the steps of forming a quasi-single crystal semiconductor material by conducting a first heat treatment on the amorphous semiconductor material and fusing and re-crystallizing part of the quasi-single crystal semiconductor material by conducting a second heat treatment.
Preferably, the second heat treatment is conducted on the quasi-single crystal semiconductor material at a temperature lower than a melting point of single crystal semiconductor material and higher than a melting point of amorphous semiconductor material. Moreover, it is preferable that only the grain boundary and the neighboring region of the quasi-single crystal semiconductor material are fused and re-crystallized by the second heat treatment.
It is preferable that the short-wavelength energy beam such as an excimer laser beam is irradiated on the quasi-single crystal semiconductor material in the second heat treatment.
The method of manufacturing a crystalline semiconductor material and a semiconductor device of the invention, is performed by heating the amorphous semiconductor material in two steps, the quasi-single crystal being formed and then part of the quasi-single crystal semiconductor material is fused and re-crystallized, whereby its crystallinity is improved.
Other and further objects, features and advantages of the invention will appear more fully from the following description.